Sustainable energy is the selection of energy sources such that they meet the needs of the present population without compromising the ability of future generations to meet their needs. A broader interpretation may allow inclusion of fossil fuels as transitional sources while technology develops, as long as new sources are developed for future generations to use. A narrower interpretation includes only energy sources which are not expected to be depleted in a time frame relevant to the human race.  This can include nuclear power, if it is utilized in a more sustainable manner than the current methods of nuclear power generation.

Sustainable energy sources are most often regarded as including all renewable sources, such as plant matter, solar power, wind power, wave power, geothermal power and tidal power. It usually also includes technologies that improve energy efficiency and energy conservation or reduction.